[Will]

Yeah, for full anti-virus suites, having more than one installed is a huge no-no. It doesn't offer any more protection, and they tend to snipe at each others definition files making all of the scanners useless. Pick one and just use that (use the TrendMicro Online scan if you think something slipped past your VScan).

Check how many fonts you have installed. Since Microsoft decided it would be a genius idea to load every single font into memory at startup, systems with many fonts installed will take longer to finish loading. Get rid of the frivolous ones, and keep the standards (Times New Roman, Courier New, Tahoma are the main ones covering serif, mono, and sans-serif).

Kill startup programs. Like SJ said, there shouldn't be much running at startup, usually just have AV/Firewall, Volume Control, and Video Driver. Using Firefox prevents the installation of random useless programs from the Internet, like IE allows.

Check virtual memory settings. If it's set to be automagically handled by Windows, that should be fine, but it could be messed up. The general rule is to have a swap file twice the size of memory (1gb in your case). Defragmenting the drive helps here too, so your disk doesn't have to jump around a lot when accessing virtual memory that is split into several sections.